HORMONES IN DIFFERENTIATION OF SEX 



A -m B 



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Fi(j. 2 2b Ihc ctlLit^ ul e i^lialiou uu llif dux uluiniuul uf the sex ducts iii the rabbit. A. 

 Persistence ot the Mullenan duct (uterine level) above, and the vaginal canal, below, in a 

 castrate male. B. The same structures seen in a castrate female as compared with tlie condi- 

 tion in the noimal female shown in C . Note almost complete involution of the male duct 

 except for remnants (CW) in the castrate male, and compare with the castrate and the 

 normal female. Castration of the female (S) has little effect on the pattern of development 

 which follows; on the other hand, castration of the male results in involution of the 

 Wolffian duct and development of the Mlillerian duct, a reversal of the normal pattern. (From 

 A. Jost, Arch. Anat. microscop. et Morphol. exper., 36, 271-315, 1947.) 



Once conditioning has occurred the effect is 

 irreversible. 



In view of the decisive role of the em- 

 bryonic testis in the development of the 

 Mlillerian ducts, as shown by castration 

 experiments, it is significant to note the con- 

 dition of the genital tracts in certain "lateral 

 gynandromorphs" of genetic origin in mice 

 (Hollander, Gowen and Stadler, 1956) which 

 have an ovary on one side of the body and 

 a testis on the other. Both gonads are usu- 

 ally small and hypoplastic. Without excep- 

 tion, however, on the side of the testis the 

 Mlillerian duct derivatives are absent en- 

 tirely and the male duct system is developed. 

 Contralaterally, a female genital tract is 

 always found although it shows great varia- 

 tion in size. An almost identical condition 

 has recently been described in a gynandro- 

 morphic hamster (Kirkman, 1958). The 

 manner in which the influence of the testis 

 tends to be limited to its own side of the 

 body in these cases is of special interest, and 

 will be considered later in dealing with the 

 localized character of hormone effects. It is 

 undoubtedly related to the early stage at 

 which the testis begins to exert its effect 

 and probably also to its reduced size in 

 nearly all cases. 



The development of the Mullenan ducts 



after isolation in vitro. At this point, in the 

 case of mammalian embryos, an obvious 

 question presents itself. Is development of 

 Mlillerian ducts in male castrates in fact a 

 purely autonomous process, due to release 

 from an inhibition normally exerted by the 

 testes or, in the absence of the gonads, does 

 some other humoral factor intervene to as- 

 sure their development? It is known that in 

 various species of mammals estrogens are 

 present in the placenta and fetal fluids in 

 considerable amounts (for references see 

 Price, 1947; Parkes, 1954), and the pos- 

 sibility arises that development of the ducts 

 after castration may be maintained under 

 the influence of an estrogenic substance of 

 nongonadal or of maternal origin. This ques- 

 tion has been answered, in the negative, 

 by experiments designed to test the self- 

 differentiating capacity of the ducts under 

 conditions of physiologic isolation. When 

 explanted in vitro (with pieces of the associ- 

 ated mesonephric bodies) the Mlillerian 

 ducts of rat embryos, regardless of the sex 

 of the donor embryo, survive and continue 

 their development in the same manner as 

 in castrate fetuses (Jost and Bergerard, 

 1949; Jost and Bozic, 1951). In these ex- 

 periments the ducts were isolated at ages 

 of 15 to 16 days, and 16 to 17 days re- 



